Relative resistance of some silkworm, Bombyx mori L. strains against bacterial flacherie under high temperature and relative humidity conditions
Relative resistance of some silkworm, Bombyx mori L. strains against bacterial flacherie under high temperature and relative humidity conditions
Sardar M. Rafique and Ghulam Ali Bajwa
ABSTRACT
Eight exotic bivoltine silkworm strains, four of Japanese origin (J-99, J-101, 205-MKD, 206-MKD), and four Chinese (C-102, 206-PO, 207-PO, 208-PO) were screened for their relative resistance against bacterial flacherie. In addition, effect of high temperature and relative humidity (rH) on the resistance of silkworm strains was also studies. The results revealed that at 25+1oC and 72+2% rH, overall mortality was significant (P0.05). 205-MKD strain was the most resistant while C-102 the least resistant with 4.0% and 10% mortality, respectively. However, difference among 205-MKD, J-99, J-101 and 208-PO was statistically non-significant. Overall mortality at higher temperature and relative humidity (30+1oC and 80+2% rH) was highly significant (P0.01). Mortality was escalated in all the test strains except 206-MKD and 206-PO Mortality increased in an array of 205-MKD (125%) > J-101 (116.67%) > 207-PO & 208-PO (66.67%)> C-102 (50%)> J-99 (33.33%)> 206-MKD & 20-6P-O (0.0%). The least susceptible strains were J-99 and 206-PO contrarily to C-102 and 207-PO, the most susceptible ones. Moreover, high temperature and relative humidity showed strong positive correlation with mortality. Outcome of the trials also indicates that Japanese silkworm strains were comparatively more resistant to bacterial flacherie than that of Chinese. On the basis of these results it is suggested that resistant silkworm strains like 205-MKD, J-99, J-101 and 208-PO should be reared at 25+1oC and 72+2% rH to override losses of cocoon crops due to bacterial flacherie.
Keywords: Silkworm, Resistance, J-99, J-101, 205-MKD, 206-MKD, C-102, 206-PO, 207-PO, 208-PO.
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June 2003
Vol. 53, Iss. 2
